1. Field of the Invention
The present general inventive concept relates to a paper pickup unit and an image forming apparatus having the same, and more particularly, to a paper pickup unit to reduce noises due to an impact between a pressing plate and a pickup roller of a main body of a paper feed unit when paper is picked up from the main body of the paper feed unit, and an image forming apparatus having the same.
2. Description of the Related Art
In general, an image forming apparatus includes a paper feed unit body for feeding a recording medium, such as a paper, at which an image is to be formed, an image forming part for forming the image on the recording medium supplied from the paper feed unit body, and a paper discharge part for discharging the recording medium, at which the image has been formed, from the image forming part.
In addition, a paper pickup unit is installed to supply the recording medium stacked on the paper feed unit body to the image forming part.
FIG. 1 illustrates a driving state of a conventional paper pickup unit 200 of an image forming apparatus.
Referring to FIG. 1, the conventional paper pickup unit 200 is installed in the image forming apparatus, which includes a shaft 201 having a pickup roller 230 for picking up a recording medium (not shown) such as a paper stacked on a pressing plate of a paper feed unit body 100, and a guide cam 210 fixedly installed at both ends of the shaft 201 to be in contact with a guide part 110 of the paper feed unit body 100.
The guide part 110 is installed on the paper feed unit body 100 and includes a guide roller 111 rotated in contact with a portion of a surface of the guide cam 210, and a guide roller housing 112 for supporting the guide roller 111.
Hereinafter, an operation of the conventional paper pickup unit 200 will be described.
When a predetermined image forming order is transmitted from a controller (not shown) in a state that the paper feed unit body 100, at which a number of sheets of paper are stacked on a pressing plate 101, is mounted on the image forming apparatus, the shaft 201 is rotated in a direction A by a driving force of a power unit 145 together with a rotation of the guide cams 210 at both ends of the shaft 201, at this time the guide roller 111 of the paper feed unit body 100 is rotated in contact with a portion of the surface of the guide cam 210 to guide a lift operation of the paper feed unit body 100 pressed upward by a compression spring 120 installed under the pressing plate 101.
In addition, the sheets stacked on the pressing plate 101 of the paper feed unit body 100 is in contact with the pickup roller 230 of the shaft 201 to rotate the pickup roller 230, thereby supplying the sheets to the image forming part (not shown) one by one.
However, when a last sheet of the paper stacked on the paper feed unit body 100 remains, a stack height of the sheets on the pressing plate is lowered, the paper feed unit body 100 is lifted by the compression spring 120, and the guide cam 210 in contact with the guide roller 111 of the paper feed unit body 100 is rotated in the direction A, as a result, the guide roller 111 is located at a lower end of the guide cam 210.
At this time, one end of a pickup housing 231 for supporting both side surfaces of the pickup roller 230 mounted on the shaft 201 collides with a portion of a surface of the lifted pressing plate 101 of the paper feed unit body 100 to generate impact noises.
In addition, when a small number of recording media are stacked on the paper feed unit body 100, the remaining small number of recording media become deviated from a conveying position of the pressing plate 101, thereby causing a paper jam or a skew phenomenon.